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Natural Dyeing: the % OWF Math

Dye guide 🧺 · Cellar crew · Nov 2026

What % OWF means, precisely

A dye or mordant dose is written as a percentage of the fiber's dry weight (OWF: "on weight of fiber"). 100 g of dry wool at 8% alum wants 8 g of alum — weigh the fiber FIRST, dry, before it has ever seen the pot. The % OWF card is the shelf version; the app's dye calculators do it live and always name the base.

Pot	Fiber 100 g	Dose	Note
Onion skins	20% dye (20 g skins… loose rule: 1:1 by weight for strong)	—	Gold-orange on protein fibers
Avocado pits	50–100% for strong pinks		Gentle simmer; pH shifts pinker
Black beans	Soak-only cold bath		Blues-greens, very pH-sensitive

Extraction

1. Chop/simmer dyestuff in water for ~1 h (or overnight soak for deeper).
2. Strain out the plant material; keep the bath at 80–90 °C for dyeing (wool and silk prefer gentler: 70–80 °C).
3. Wet the fiber WELL before it meets the bath — dry spots dye uneven.

Mordanting, briefly

• Alum 8–15% OWF: the standard workhorse; dissolve hot, hold fiber at 80 °C for 30–60 min.
• Iron 1–2% OWF: shifts toward grays/darks; too much embrittles fiber.
• Tannin 5–10%: the plant mordant for cotton before alum (tea, oak gall).

The swatch diary

Natural dye repeats only when it's written. One swatch per attempt: fiber weight, dyestuff + weight, mordant + %, tap-water pH, time, temperature — then tape the swatch beside it. A year in, the diary is the recipe book, and it never lies. The app's dye calculator logs the same fields per batch.

Fixes

Symptom	Cause	Fix
Pale result	Weak extraction or under-dosed	Simmer dyestuff longer; re-enter the bath for a second pass
Color rinses away	No mordant or wrong fiber	Cellulose fibers need tannin + alum; protein fibers want alum
Everything's gray	Iron contamination in pot/water	Stainless pot, not cast iron; check tap water